1. Field of the Invention
The present invention relates to a liquid heating apparatus, more particularly to a liquid heating apparatus of the type in which a pulse combustion burner is mounted to a liquid vessel to heat an amount of liquid such as cooking oil or other fluid medium stored therein.
2. Description of the Prior Art
In such a conventional liquid heating apparatus as described above, the liquid vessel is assembled within a support frame, and the pulse combustion burner includes a combustion chamber secured at its inlet end to an internal surface of a forward side wall of the vessel in a liquid-tight manner and immersed in liquid in the vessel. The combustion chamber of the burner has an exhaust port connected to a tailpipe the great part of which is immersed in the liquid. The tailpipe extends outwardly through a rearward side wall or bottom wall of the vessel and is connected at its exhaust end to a muffler assembly which is fixedly mounted in place within the support frame in a non-exchangeable manner.
During operation of the pulse combustion burner, medium and high frequency noises are caused by impact sounds of flapper valves in an air-fuel mixer head of the burner and mechanical vibration of other component parts of the burner. Additionally, low frequency noises are caused by pulse combustion in the combustion chamber. For effective reduction of the medium and high frequency noises, it is desirable to adapt a muffler of the expansion and resonance type to the burner. For reduction of the low frequency noises, it is desirable to adapt a resonance type muffler to the burner. The noise reduction range of the resonance type muffler is, however, very narrow. On the other hand, the combustion frequency of the burner will change in a range of approximately 80-100 hertzs in accordance with the component of used gaseous fuel. In the case that the used gaseous fuel contains a relatively large amount of hydrogen components, the combustion frequency of the burner becomes large. For this reason, such a resonance type muffler as described above does not effect to reduce the low frequency noises in accordance with the component of used gaseous fuel.